Time-of-Use Rate Savings Calculator
Calculate monthly electricity bill savings by shifting loads from peak to off-peak hours.
Enter kWh usage, percentage shifted, and peak versus off-peak rates.
Time-of-use (TOU) pricing charges more for electricity used during peak demand hours and less during off-peak periods. Many utilities offer these plans, and smart meters make them practical.
Typical peak hours: 4 PM to 9 PM on weekdays (varies by utility). Typical off-peak hours: nights and weekends. Some utilities add a “super off-peak” window (midnight to 6 AM) at even lower rates, often designed specifically for EV charging.
The math
On-peak kWh = total kWh x (1 - shift_fraction)
Off-peak kWh = total kWh x shift_fraction
Original bill = total kWh x peak_rate (assuming you were previously using a flat rate equal to the peak rate)
New TOU bill = (on-peak kWh x peak_rate) + (off-peak kWh x off-peak_rate)
Monthly savings = original bill - new TOU bill
What loads can shift
EV charging is the biggest lever. Charging overnight instead of after work is exactly what TOU plans are designed to incentivize. A 40 kWh charge at $0.40/kWh peak costs $16; at $0.12/kWh super off-peak it costs $4.80 — a $11.20 saving on one charge.
Dishwashers and clothes washers with delay-start features are easy wins. Pool pump timers are another. Water heaters can run on timers if the tank is large enough to carry heat through peak hours.
Loads that are hard to shift: cooking, showers, lighting. The savings from TOU mainly come from the high-draw, time-flexible loads.
Pitfalls
Peak rates on TOU plans are often higher than flat rates. If you cannot shift much usage, you may pay more on TOU than on a flat rate. Run the numbers before switching.